U.S. patent application number 11/969244 was filed with the patent office on 2009-07-09 for automatic clustering of wireless network nodes toward selected mesh access points.
Invention is credited to Stefano Alessandro Crosta, Vincent Jean Ribiere, Pascal THUBERT, Patrick Wetterwald.
Application Number | 20090175208 11/969244 |
Document ID | / |
Family ID | 40844481 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090175208 |
Kind Code |
A1 |
THUBERT; Pascal ; et
al. |
July 9, 2009 |
Automatic Clustering of Wireless Network Nodes Toward Selected Mesh
Access Points
Abstract
In one embodiment, a method comprises detecting by a mesh access
point a number of wireless network nodes that are attached to the
mesh access point within a mesh network; calculating by the mesh
access point an attachment preference factor that enables at least
one other wireless network node to determine whether to attach to
the mesh access point, wherein the mesh access point increases the
attachment preference factor based on a corresponding increase in
the number of wireless network nodes that are attached to the mesh
access point; and outputting by the mesh access point the
attachment preference factor, enabling the at least one other
wireless network node to determine whether to attach to the mesh
access point.
Inventors: |
THUBERT; Pascal; (La Colle
Sur Loup, FR) ; Wetterwald; Patrick; (Mouans Sartoux,
FR) ; Ribiere; Vincent Jean; (Biot, FR) ;
Crosta; Stefano Alessandro; (Biot, FR) |
Correspondence
Address: |
LEON R TURKEVICH
2000 M STREET NW, 7TH FLOOR
WASHINGTON
DC
200363307
US
|
Family ID: |
40844481 |
Appl. No.: |
11/969244 |
Filed: |
January 4, 2008 |
Current U.S.
Class: |
370/312 ;
370/338 |
Current CPC
Class: |
H04W 48/08 20130101;
H04W 28/16 20130101 |
Class at
Publication: |
370/312 ;
370/338 |
International
Class: |
H04H 20/71 20080101
H04H020/71; H04Q 7/24 20060101 H04Q007/24 |
Claims
1. A method comprising: detecting by a mesh access point a number
of wireless network nodes that are attached to the mesh access
point within a mesh network; calculating by the mesh access point
an attachment preference factor that enables at least one other
wireless network node to determine whether to attach to the mesh
access point, wherein the mesh access point increases the
attachment preference factor based on a corresponding increase in
the number of wireless network nodes that are attached to the mesh
access point; and outputting by the mesh access point the
attachment preference factor, enabling the at least one other
wireless network node to determine whether to attach to the mesh
access point.
2. The method of claim 1, wherein: the attachment preference factor
is expressed as at least one of a cost factor or an ease factor;
the cost factor identifying the attachment preference factor as a
corresponding cost for the at least one other wireless network node
to attach to the mesh access point; the ease factor identifying the
attachment preference factor as a corresponding ease for the at
least one other wireless network node to attach to the mesh access
point.
3. The method of claim 1, further comprising determining, by the
mesh access point, a signal strength of a wireless signal
transmitted by an attachment access point used by the mesh access
point, the calculating including increasing the attachment
preference factor based on a corresponding increase in the signal
strength.
4. The method of claim 3, wherein the attachment preference factor
is based on: applying a first influence rate to the number of
wireless network nodes that are attached to the mesh access point;
and applying a second influence rate to the signal strength, the
first influence rate greater than the second influence rate.
5. The method of claim 4, further comprising: determining by the
mesh access point a depth of the mesh access point relative to a
centralized access point within the mesh network; wherein the
attachment preference factor is based on applying a third influence
rate to the depth, the third influence rate less than the second
influence rate, the calculating including increasing the attachment
preference factor based on a corresponding increase in the
depth.
6. The method of claim 1, further comprising: determining by the
mesh access point a depth of the mesh access point relative to a
centralized access point within the mesh network; wherein the
attachment preference factor is based on applying a first influence
rate to the number of wireless network nodes that are attached to
the mesh access point, and applying a second influence rate to the
depth, the second influence rate less than the first influence
rate; wherein the calculating includes increasing the attachment
preference factor based on a corresponding increase in the
depth.
7. The method of claim 1, wherein the outputting includes
outputting a mesh advertisement message that specifies the
attachment preference factor.
8. The method of claim 1, further comprising: receiving by the mesh
access point a multicast packet from a centralized access point
within the mesh network; and the mesh access point suppressing
retransmission of the multicast packet into the mesh network if the
number of wireless network nodes that are attached to the mesh
access point equals zero.
9. The method of claim 1, further comprising: receiving by the mesh
access point a minimum attachment preference factor from a
centralized access point in the mesh network; wherein the
calculating includes calculating the attachment preference factor
relative to the minimum attachment preference factor.
10. An apparatus comprising: an attachment preference calculation
circuit configured for detecting a number of wireless network nodes
that are attached to the apparatus within a mesh network,
calculating an attachment preference factor that enables at least
one other wireless network node to determine whether to attach to
the apparatus, and increasing the attachment preference factor
based on detecting a corresponding increase in the number of
wireless network nodes that are attached to the apparatus; and a
network interface circuit configured for outputting the attachment
preference factor, enabling the at least one other wireless network
node to determine whether to attach to the apparatus.
11. The apparatus of claim 10, wherein: the attachment preference
factor is expressed as at least one of a cost factor or an ease
factor; the cost factor identifying the attachment preference
factor as a corresponding cost for the at least one other wireless
network node to attach to the apparatus; the ease factor
identifying the attachment preference factor as a corresponding
ease for the at least one other wireless network node to attach to
the apparatus.
12. The apparatus of claim 10, wherein the network interface
circuit is configured for determining a signal strength of a
wireless signal transmitted by an attachment access point used by
the apparatus, the attachment preference calculation circuit
configured for increasing the attachment preference factor based on
a corresponding increase in the signal strength.
13. The apparatus of claim 12, wherein the attachment preference
calculation circuit is configured for calculating the attachment
preference factor based on: applying a first influence rate to the
number of wireless network nodes that are attached to the
apparatus; and applying a second influence rate to the signal
strength, the first influence rate greater than the second
influence rate.
14. The apparatus of claim 13, wherein the attachment preference
calculation circuit is configured for: determining a depth of the
apparatus relative to a centralized access point within the mesh
network; calculating the attachment preference factor based on
applying a third influence rate to the depth, the third influence
rate less than the second influence rate; and increasing the
attachment preference factor based on a corresponding increase in
the depth.
15. The apparatus of claim 10, wherein the attachment preference
calculation circuit is configured for: determining a depth of the
apparatus relative to a centralized access point within the mesh
network; calculating the attachment preference factor based on
applying a first influence rate to the number of wireless network
nodes that are attached to the apparatus, and applying a second
influence rate to the depth, the second influence rate less than
the first influence rate; and increasing the attachment preference
factor based on a corresponding increase in the depth.
16. The apparatus of claim 10, wherein the network interface
circuit is configured for outputting a mesh advertisement message
that specifies the attachment preference factor.
17. The apparatus of claim 10, wherein: the network interface
circuit is configured for receiving a multicast packet from a
centralized access point within the mesh network; the attachment
preference calculation circuit is configured for suppressing
retransmission of the multicast packet into the mesh network if the
number of wireless network nodes that are attached to the apparatus
equals zero.
18. The apparatus of claim 10, wherein: the network interface
circuit is configured for receiving a minimum attachment preference
factor from a centralized access point in the mesh network; the
attachment preference calculation circuit is configured for
calculating the attachment preference factor relative to the
minimum attachment preference factor.
19. An apparatus comprising: means for detecting a number of
wireless network nodes that are attached to the apparatus within a
mesh network, the means for detecting further configured for
calculating an attachment preference factor that enables at least
one other wireless network node to determine whether to attach to
the apparatus, and increasing the attachment preference factor
based on detecting a corresponding increase in the number of
wireless network nodes that are attached to the apparatus; and
means for outputting the attachment preference factor, enabling the
at least one other wireless network node to determine whether to
attach to the apparatus.
Description
TECHNICAL FIELD
[0001] The present disclosure generally relates to deploying a
wireless local area network (WLAN) using wireless link protocols,
such as IEEE 802.11e and IEEE P802.11s/D.100 wireless Ethernet,
based on implementing a mesh network having distributed mesh points
in communication with a mesh portal having a wired link to a wide
area network.
BACKGROUND
[0002] Wireless local area networks are being deployed in
large-scale service areas using mesh networking. Mesh networking
can utilize mesh points (MPs) to establish a mesh backhaul
infrastructure. For example, the IEEE P802.11s/D1.00 specification
describes mesh points as devices that support WLAN mesh services,
i.e. they participate in the formation and operation of the mesh
network. The mesh points can establish a mesh backhaul
infrastructure based on establishing peer-to-peer wireless links
between each mesh point, and establishing a tree topology that is
"rooted" by a "mesh portal": the mesh portal is a mesh point that
has a wired link for reaching a wide area network. Mesh points that
also serve as "access points" for wireless client devices are
referred to as "Mesh Access Points" (MAPs). The distribution of the
mesh points can extend wireless coverage of the WLAN over a larger
coverage area for wireless user devices.
[0003] Mesh networking utilizes routing protocols that enable mesh
path selection and forwarding of data packets at the link layer.
For example, the IEEE P802.11s specification defines a default
mandatory routing protocol (Hybrid Wireless Mesh Protocol, or
HWMP). Another example mesh network utilizes a protocol known as
Adaptive Wireless Path Protocol (AWP), available for example in the
commercially available Cisco Aironet 1500 Series Outdoor Mesh
Access Point by Cisco Systems, San Jose, Calif.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Reference is made to the attached drawings, wherein elements
having the same reference numeral designations represent like
elements throughout and wherein:
[0005] FIG. 1 illustrates an example mesh network having mesh
access points choosing attachment preference factors for clustering
of wireless network nodes, according to an example embodiment.
[0006] FIG. 2 illustrates an example mesh access point from the
system of FIG. 1, according to an example embodiment.
[0007] FIG. 3 illustrates an example method in the mesh network of
clustering wireless network nodes, according to an example
embodiment.
DESCRIPTION OF EXAMPLE EMBODIMENTS
Overview
[0008] In one embodiment, a method comprises detecting by a mesh
access point a number of wireless network nodes that are attached
to the mesh access point within a mesh network; calculating by the
mesh access point an attachment preference factor that enables at
least one other wireless network node to determine whether to
attach to the mesh access point, wherein the mesh access point
increases the attachment preference factor based on a corresponding
increase in the number of wireless network nodes that are attached
to the mesh access point; and outputting by the mesh access point
the attachment preference factor, enabling the at least one other
wireless network node to determine whether to attach to the mesh
access point.
[0009] In another embodiment, an apparatus comprises an attachment
preference calculation circuit and a network interface circuit. The
attachment preference calculation circuit is configured for
detecting a number of wireless network nodes that are attached to
the apparatus within a mesh network. The attachment preference
calculation circuit also is configured for calculating an
attachment preference factor that enables at least one other
wireless network node to determine whether to attach to the
apparatus. The attachment preference calculation circuit also is
configured for increasing the attachment preference factor based on
detecting a corresponding increase in the number of wireless
network nodes that are attached to the apparatus. The network
interface circuit is configured for outputting the attachment
preference factor, enabling the at least one other wireless network
node to determine whether to attach to the apparatus.
DETAILED DESCRIPTION
[0010] Particular embodiments disclosed herein enable wireless
network nodes (e.g., mesh access points or wireless host nodes)
within a mesh network to automatically attach to a mesh access
point (MAP) according to a clustered topology that minimizes
overlapping transmission areas between neighboring mesh access
points. Each mesh access point can calculate an attachment
preference factor based on a detected number of wireless network
nodes that are attached to the mesh access point. A wireless
network node that is attached to a mesh access point also is
referred to herein as "an attached wireless network node". If a
mesh access point has a greater number of attached wireless network
nodes (i.e., wireless network nodes that are attached to the mesh
access point), the mesh access point will calculate (i.e.,
generate) a corresponding higher attachment preference factor;
conversely, if a mesh access point has a lesser number of attached
wireless network nodes, the mesh access point will calculate a
corresponding lower attachment preference factor. Hence, a mesh
access point having no attached wireless network nodes will
generate a minimum attachment preference factor.
[0011] Each wireless network node can be configured for selecting
an attachment access point from among multiple advertising mesh
access points based on attaching to the mesh access point
advertising the highest corresponding attachment preference factor.
The attachment preference factor advertised by a mesh access point
can be expressed for example as a cost factor for attaching to the
mesh access point (e.g., a higher preference factor can be
implemented as a lower cost factor), and/or an ease factor in
attaching to the mesh access point (e.g., a higher preference
factor can be implemented as a higher ease factor).
[0012] Hence, the particular embodiments can cause wireless network
nodes to prefer attaching to a mesh access point having a larger
number of wireless network nodes that already are attached,
resulting in clustering of wireless network nodes about a given
mesh access point. Hence, wireless network nodes can migrate from
mesh access points having a fewer number of attached wireless
network nodes toward mesh access points having more attached
wireless network nodes. Consequently, any mesh access point that
has no attached wireless node no longer needs to retransmit a
received multicast packet, and can therefore suppress
retransmission of received multicast packets to prevent
interference with a neighboring mesh access point that has attached
wireless network nodes within a given transmission area. Hence, the
number of multicast transmissions within a mesh network can be
reduced.
[0013] Hence, the particular embodiments minimize interference
between neighboring mesh access points during retransmission of
multicast packets from a centralized access point in the mesh
network (e.g., a rooftop access point) by enabling clustering
around certain mesh access points, enabling the elimination of
interference by neighboring mesh access points that have no
attached wireless network nodes. The elimination of interference by
neighboring mesh access points is particularly effective for
retransmission of wireless data packets that do not follow a
carrier sense multiple access with collision avoidance (CSMA/CA)
protocol, for example multicast packets transmitted according to
IEEE P802.11s.
[0014] FIG. 1 illustrates an example wireless mesh network 10
having multiple mesh access points (e.g., P1, P2, P3, P4, and P5)
12 and other wireless network nodes (e.g., wireless host devices
and/or other mesh access points) 14, according to an example
embodiment. Each of the mesh access points 12 can generate a
corresponding attachment preference factor (AF) 36, illustrated in
FIG. 2, that enables the wireless network nodes 14 to automatically
cluster toward selected mesh access points 12. The mesh access
points 12 provide connectivity for the attached wireless network
nodes 14 to a wired local area network 18 based on wireless
connections 24 with a centralized access point 16, also referred to
as a "mesh portal" 16 or a "rooftop access point" (RAP) 16. As used
herein, the term "centralized access point" refers to an access
point that serves at least as a root of a multicast tree for
transmission of multicast packets within a multicast domain. The
centralized access point 16 can be implemented as a wired mesh
access point having a wired connection to the wired local area
network (e.g., an IEEE 802.3 LAN) 18, serving as a root for
wireless network nodes 12 and 14 that do not have a wired
connection. The centralized access point 16 also can provide a
wired connection to a wide area network (WAN) 20 and/or a wired
device 22 (e.g., a mesh controller) via the LAN 18.
[0015] Each of the mesh access points 12 and the wireless network
nodes 14 can communicate with the centralized access point 16 via
wireless mesh links 24 established between the mesh access points
12 and the centralized access point 16. Each mesh access point
(MAP) 12 (and/or 14, if a wireless network node is implemented as a
mesh access point) can be implemented for example based on the
commercially-available Cisco Aironet Series 1500 Mesh Access Point
from Cisco Systems, San Jose, Calif., and based on applying the
features described herein. Each MAP 12 (and/or 14, as appropriate)
can be controlled by a mesh controller 22 within the wired LAN 18
according to a prescribed lightweight access point protocol, for
example a Lightweight Access Point Protocol (LWAPP) commercially
available from Cisco Systems, Inc., San Jose, Calif., and described
in the Internet Engineering Task Force (IETF) Internet Draft by
Calhoun et al., entitled "Light Weight Access Point Protocol",
available via the World Wide Web at the site address
"ietf.org/internet-drafts/draft-ohara-capwap-lwapp-04.txt".
[0016] The wireless mesh network 10 also can be implemented
according to existing wireless protocols as promulgated by the
Institute for Electrical and Electronic Engineers (IEEE), including
IEEE 802.11, IEEE 802.11e and the proposed P802.11s/D1.00. In
particular, the wireless nodes 12 and 14 can be implemented using a
well-known physical layer (layer 1) and link layer (layer 2)
protocol according to the Open Systems Interconnection (OSI)
Reference Model: an example protocol is the IEEE 802.11
Specification, which was published by the Institute of Electrical
and Electronics Engineers (IEEE) as "IEEE 802.11, Wireless LAN
Medium Access Control (MAC) and Physical Layer (PHY)
specifications," Standard, IEEE, New York, N.Y., August 1999.
[0017] The IEEE also published numerous supplements to the IEEE
802.11 specification, for example the IEEE 802.11a specification,
the IEEE 802.11b specification, and the IEEE 802.11e specification,
published Nov. 11, 2005 as "IEEE Std 802.11e-2005, IEEE Standard
for Information Technology--Telecommunications and Information
Exchange Between Systems--Local and Metropolitan Area
Networks--Specific Requirements Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY) Specifications--Amendment 8:
Medium Access Control (MAC) Quality of Service (QoS)Enhancements"
(ISBN 0-7381-4772-9) (referred to herein as "the IEEE 802.11e
specification").
[0018] The IEEE also published a proposed standard referred to as
IEEE 802.11s and/or IEEE 802.11s/D1.00, published November 2006 as
"IEEE P802.11s.TM./D1.00 Draft Amendment to Standard for
Information Technology--Telecommunications and Information Exchange
Between Systems-LAN/MAN Specific Requirements--Part 11: Wireless
Medium Access Control (MAC) and physical layer (PHY)
specifications: Amendment: ESS Mesh Networking".
[0019] The IEEE 802.11e specification specifies transmitting
packets using a Carrier Sense Multiple Access with Collision
Avoidance (CSMA/CA) mechanism. For example, a first station that
has a packet to transmit determines if the wireless transmission
medium is in use, i.e., if any data is currently being transmitted
on the wireless transmission medium. If the medium is in use by a
second station, the first station defers its transmission until
detecting that the wireless medium is quiescent (i.e., is not
currently transmitting any data; inactive) for at least a
prescribed time interval. The first station can begin transmitting
its data packet on the wireless transmission medium only after the
medium has been quiescent for at least the prescribed time
interval. The CSMA/CA mechanism is used only for unicast packet
transmission, however, hence other wireless data packet traffic
such as multicast packets or anycast packets can be retransmitted
by the wireless network nodes 12 or 14 without relying on the
collision avoidance mechanism.
[0020] Hence, if each of the mesh access points 12 receives a
multicast packet from the centralized access point 16 in the
wireless mesh network 10, the mesh access points 12 having
overlapping transmission areas will encounter collisions upon
retransmitting the same multicast packet at the same time.
[0021] According to the example embodiments described herein, each
mesh access point 12 can calculate a corresponding attachment
preference factor (AF) 36, illustrated in FIG. 2, that can be used
by at least one other wireless network node 14 for selectively
attaching to the corresponding mesh access point 12. Each wireless
network node 14, in response to receiving mesh advertisement
messages from multiple mesh access points 12 advertising respective
attachment preference factors (AF), can determine whether to attach
to a given mesh access point 12 based on its corresponding
attachment preference factor (AF). Hence, a given wireless network
node 14 can selectively attach to the one mesh access point 12
advertising the highest attachment preference factor (AF) from
among the mesh advertisement messages received by the wireless
network node 14. Moreover, each mesh access point 12 can increase
its attachment preference factor (AF) based on a corresponding
increase in the number (N) of attached wireless network nodes.
Consequently, mesh access points (e.g., "P1", "P3", "P5") 12 having
a greater number of currently-attached wireless network nodes can
advertise a higher attachment preference factor (AF) relative to
other mesh access points (e.g., "P2", "P4") 12 that have fewer or
no attached wireless network nodes 14. The higher attachment
preference factors (AF) advertised by the mesh access points "P1",
"P3", "P5" (i.e., "preferred mesh access points") 12 also can cause
wireless network nodes 14 that are attached to the other mesh
access points "P2" or "P4" 12 having lower respective attachment
preference factors (i.e., "lesser mesh access points") to migrate
to the preferred mesh access points "P1", "P3", "P5" by attaching
to one of the preferred mesh access points, including registering
with the preferred mesh access point, and detaching from the lesser
mesh access point (e.g., passively by ceasing communications with
the lesser mesh access points, or actively by sending a de-register
message). The registration by the wireless network node 14 with the
preferred mesh access point (e.g., "P1", "P3", or "P5") causes that
preferred mesh access point to further increase its corresponding
attachment preference factor (AF).
[0022] Hence, any mesh access point (e.g., "P2", "P4") 12 that does
not have any attached wireless network node 14 can suppress
retransmission of a multicast packet or anycast packet transmitted
by the centralized access point 16, in order to avoid interference
with neighboring mesh access points (e.g., "P1", "P3", "P5") 12
that have attached wireless network nodes 14.
[0023] The attachment preference factors (AF) calculated by each of
the mesh access points 12 can be calculated automatically, such
that the attachment preference factors (AF) are updated based on
the random attachments by the wireless network nodes 14, as well as
other parameters such as signal strength or depth of the mesh
access point 12. For example, the attachment preference factor (AF)
can be adjusted based on various factors including received signal
strength indicator (RSSI), or received channel power indicator
(RCPI) as described in the IEEE 802.11k. The IEEE P802.11s
specification also describes an airtime link metric computation
procedure that reflects the amount of channel resources consumed by
transmitting the frame over a particular link, measured in terms of
bit rate and frame error rate for a given test frame size.
[0024] The attachment preference factor (AF) also can be calculated
by each mesh access point 12 based on a corresponding minimum
preference value (Min) supplied for example by a controller 22,
enabling the controller 22 to add a bias towards selected mesh
access points 12.
[0025] FIG. 2 illustrates an example mesh access point 12,
according to an example embodiment. The mesh access point 12
includes a wireless network interface circuit 30, an attachment
preference calculation circuit 32, and a memory circuit 34.
[0026] The wireless network interface circuit 30, implemented for
example according to IEEE 802.11, IEEE 802.11e, and IEEE P802.11s,
can include one or more physical layer (PHY) transceiver circuits
38 and a Carrier Sense with Multiple Access and Collision Avoidance
(CSMA/CA) circuit (not shown) for unicast packets. The physical
layer transceiver circuit 38 can be configured for detecting the
received signal strength of a received data packet on a wireless
link 24, and outputting for the wireless network interface circuit
30 a corresponding received signal strength indicator (RSSI);
alternately, the physical layer transceiver circuit 38 also can
detect and report a received channel power indicator (RCPI) value.
Each physical layer transceiver circuit 30 can be configured for
transmitting and receiving on a corresponding wireless channel
(e.g., Channel A or Channel B); for example, the mesh access point
(e.g., "P1") 12 can be configured for sending and receiving data to
and from the centralized access point 16 via a first channel (e.g.,
Channel A), and sending and receiving data to and from each
attached wireless network node (e.g., C1, C2, C3, C4, C5) 14 via a
second channel (e.g. Channel B). In this example, each of the mesh
access points 12 can communicate with the centralized access point
16 via "Channel A", and with their respective attached wireless
network nodes 14 via "Channel B".
[0027] As described in further detail below with respect to FIG. 3,
the attachment preference calculation circuit 32 within the mesh
access point 12 can be configured for detecting the number (N) 40
of wireless network nodes 14 that are attached to the mesh access
point 12 (i.e., the number of attached wireless network nodes). For
example, FIG. 1 illustrates that the wireless network nodes "C1",
"C2", "C3", "C4", and "C5" 14 currently are attached to the mesh
access point "P1" 12. Hence, the attachment preference calculation
circuit 32 within the mesh access point "P1" 12 can detect the
number (N) of wireless network nodes 14 that are attached to the
mesh access point "P1" (i.e., "C1", "C2", "C3", "C4", and "C5") as
equal to five ("5").
[0028] The attachment preference calculation circuit 32 in the mesh
access point 12 also can calculate the attachment preference factor
(AF) based on the number (N) of wireless network nodes 14 that are
attached to the mesh access point 12. The attachment preference
calculation circuit 32 also can be configured for suppressing
retransmission of a multicast packet, received from the centralized
access point 16, based on determining the number (N) of attached
wireless network nodes 14 equals zero.
[0029] The memory circuit 34 can be configured for storing various
parameters used by the attachment preference calculation circuit 32
in calculating the attachment preference factor (AF). As
illustrated in FIG. 2, the memory circuit 34 can be configured for
storing the attachment preference factor (AF) 36, the number (N) 40
of attached wireless network nodes, a minimum preference value
(Min) 42, and a depth (D) of the mesh access point 12 relative to
the centralized access point 16.
[0030] The memory circuit 34 also can be configured for storing
various influence factors representing respective rates of
influence for parameters used in calculating the attachment
preference factor (AF) 36. For example, the memory circuit 34 can
be configured for storing a node influence factor (kN) 46
representing a corresponding influence rate for adding the number
of attached wireless network nodes 40 to the attachment preference
factor (AF) 36. The memory circuit 34 also can be configured for
storing a signal influence factor (kS) 48 representing a
corresponding influence rate for adding the corresponding signal
strength (e.g. as detected by the corresponding PHY transceiver 38
in communication with its corresponding attachment mesh point). The
memory circuit 34 also can be configured for storing a depth
influence factor (kD) 50 representing a corresponding influence
rate for adding the corresponding depth 44 to the attachment
preference factor (AF) 36. As illustrated in FIG. 2, the node
influence factor 46 can be greater than the signal influence factor
46, and the signal influence factor 48 can be greater than the
depth influence factor; hence, the number (N) 40 of attached
wireless network nodes can have the greatest influence on the
attachment preference factor (AF) 36, the signal strength (measured
by the transceiver 38) from the attachment mesh point (e.g., the
rooftop access point 16) can have the next greatest influence on
the attachment preference factor (AF) 36, and the depth 44 of the
mesh access point 12 can have the least influence on the attachment
preference factor (AF) 36. The memory circuit 34 also can be
configured for storing other various parameters (not shown).
[0031] Any of the disclosed circuits of the mesh access point 12
(including the network interface circuit 30, the attachment
preference calculation circuit 32, and the memory circuit 34), or
any of the attached wireless network nodes 14, can be implemented
in multiple forms. Example implementations of the disclosed
circuits include hardware logic that is implemented in a logic
array such as a programmable logic array (PLA), a field
programmable gate array (FPGA), or by mask programming of
integrated circuits such as an application-specific integrated
circuit (ASIC). Any of these circuits also can be implemented using
a software-based executable resource that is executed by a
corresponding internal processor circuit such as a microprocessor
circuit (not shown), where execution of executable code stored in
an internal memory circuit (e.g., within the memory circuit 34)
causes the processor circuit to store application state variables
in processor memory, creating an executable application resource
(e.g., an application instance) that performs the operations of the
circuit as described herein. Hence, use of the term "circuit" in
this specification refers to both a hardware-based circuit that
includes logic for performing the described operations, or a
software-based circuit that includes a reserved portion of
processor memory for storage of application state data and
application variables that are modified by execution of the
executable code by a processor. The memory circuit 34 can be
implemented, for example, using a non-volatile memory such as a
programmable read only memory (PROM) or an EPROM, and/or a volatile
memory such as a DRAM, etc.
[0032] Further, any reference to "outputting a message" or
"outputting a packet" (or the like) can be implemented based on
creating the message/packet in the form of a data structure and
storing that data structure in a tangible memory medium in the
disclosed apparatus (e.g., in a transmit buffer). Any reference to
"outputting a message" or "outputting a packet" (or the like) also
can include electrically transmitting (e.g., via wired electric
current or wireless electric field, as appropriate) the
message/packet stored in the tangible memory medium to another
network node via a communications medium (e.g., a wired or wireless
link, as appropriate) (optical transmission also can be used, as
appropriate). Similarly, any reference to "receiving a message" or
"receiving a packet" (or the like) can be implemented based on the
disclosed apparatus detecting the electrical (or optical)
transmission of the message/packet on the communications medium,
and storing the detected transmission as a data structure in a
tangible memory medium in the disclosed apparatus (e.g., in a
receive buffer). Also note that the memory circuit 34 can be
implemented dynamically by the attachment preference calculation
circuit 32, for example based on memory address assignment and
partitioning executed by the attachment preference calculation
circuit 32.
[0033] FIG. 3 illustrates an example method for enabling a mesh
access point 12 to automatically calculate an attachment preference
factor (AF) that enables automatic clustering of wireless network
nodes to selected mesh access points, according to an example
embodiment. The steps described in FIG. 3 can be implemented as
executable code stored on a computer readable medium (e.g., floppy
disk, hard disk, ROM, EEPROM, nonvolatile RAM, CD-ROM, etc.) that
are completed based on execution of the code by a processor; the
steps described herein also can be implemented as executable logic
that is encoded in one or more tangible media for execution (e.g.,
programmable logic arrays or devices, field programmable gate
arrays, programmable array logic, application specific integrated
circuits, etc.).
[0034] As described previously, each mesh access point 12 can
automatically begin calculating an attachment preference factor
(AF) 36, or can calculate the attachment preference factor (AF) 36
based on a received minimum attachment preference value (Min) 42
that can bias the mesh access point 12 accordingly. For example, if
the mesh access points 12 are configured for receiving minimum
attachment preference values 42, a controller 22 can generate the
respective minimum attachment preference values 42 in step 60, for
example based on identifying overlapping propagation areas, and
identifying preferred broadcast points and interfering broadcast
points.
[0035] For example, assume in FIG. 1 that: the mesh access points
"P1" and "P2" have an overlapping propagation area (identified as
"P1-P2"); the mesh access points "P2" and "P3" have an overlapping
propagation area (identified as "P2-P3"); the mesh access points
"P3" and "P4" have an overlapping propagation area (identified as
"P3-P4"); and the mesh access points "P4" and "P5" have an
overlapping propagation area (identified as "P4-P5"). If the
attached wireless network nodes 14 were evenly distributed among
the mesh access points 12, numerous collisions would be encountered
each time the mesh access points 12 attempted to retransmit a
multicast packet received from the centralized access point 16.
Hence, the controller 22 (or a network administrator that is
configuring the network 10 via the controller 22) can identify in
step 60 the mesh access points "P1" and "P5" as preferred broadcast
points based on having the maximum number of non-overlapping
transmission areas (i.e., minimum number of overlapping
transmission areas), and "P3" based on not interfering with the
preferred broadcast points "P1" and "P5". Similarly, the mesh
access points "P2" and "P4" can be identified in step 60 by the
mesh controller 22 as interfering broadcast points based on the
overlapping transmission or propagation areas.
[0036] Hence, the mesh controller 22 can send in step 62 minimum
preference values 42 to each of the mesh access points 12, where
the preferred broadcast points (e.g., "P1", "P3", and "P5") can
receive minimum preference values 42 that are greater than the
respective minimum preference values 42 assigned to the interfering
broadcast points (e.g., "P2", "P4").
[0037] Referring to step 64, each mesh access point (e.g., "P1") 12
can determine whether a received minimum preference value 42 is
received from the mesh controller 22. As described previously, the
attachment preference calculation circuit 32 can independently
generate its own attachment preference factor (AF) 36, without the
necessity of any bias introduced by the minimum preference value 42
from the controller 22. If, however, a minimum preference value is
received by the wireless network interface circuit 30 of the mesh
access point 12, the attachment preference calculation circuit 32
stores in step 66 the minimum preference value 42 into the memory
circuit 34.
[0038] As described below, the attachment preference calculation
circuit 32 can generate mesh advertisement messages that specify
the corresponding attachment preference factor (AF) 36: if any
attached wireless network nodes 14 are detected by the attachment
preference calculation circuit 32 (e.g., based on receiving a
registration from the attached wireless node), the attachment
preference calculation circuit 32 can register in step 68 the
attached wireless network nodes 14, and update the number (N) 40 of
attached wireless nodes.
[0039] The attachment preference calculation circuit 32 calculates
in step 70 the attachment preference factor (AF) 36 based on the
number (N) 40 of attached wireless nodes 14. For example, the
attachment preference calculation circuit 32 can determine in step
70 the number (N) of attached wireless nodes 40, the signal
strength "S" (e.g., RSSI, RCPI, etc.) of the wireless signal
transmitted by the corresponding attachment access point (e.g., the
rooftop access point 16), and the corresponding depth (D) 44 of the
mesh access point 12 relative to the centralized access point 16.
The attachment preference calculation circuit 32 also can apply in
step 70 the respective influence factors 46, 48, and 50 to the
number (N) of attached wireless nodes 40, the signal strength "S"
of the wireless signal transmitted by the attachment access point
(e.g., RAP 16), and the depth (D) 44. Assuming no bias is added by
the mesh controller 22, the attachment preference calculation
circuit 32 can calculate the attachment preference factor (AF) 36
based on the weighted values of the number of attached nodes
(kN*N), the weighted signal strength (kN*N), and the weighted depth
(kD*D). If the mesh access point 12 has received a bias value 42
from the mesh controller 22, the attachment preference calculation
circuit 32 also can add the bias value 42 to the attachment
preference factor (AF) 36.
[0040] The attachment preference calculation circuit 32 can
generate in step 72 a mesh advertisement message for output by the
wireless network interface circuit 30 on the channel (e.g., Channel
B) serving wireless network nodes seeking to selectively attach to
the mesh access point "P1" 12. The mesh advertisement message
output in step 72 can specify the attachment preference factor (AF)
36 either in the form of an "ease" factor identifying a
corresponding ease in attaching to the mesh access point "P1" 12
relative to the RAP 16, or in the form of a cost for attaching to
the mesh access point "P1" 12. As will become apparent, the
attachment preference factor (AF) 36 also can be based on an
aggregation of other cost or ease factors of "upstream" attachment
points relied upon in reaching the centralized access point 16.
[0041] Hence, each mesh access point within the mesh network 10 can
calculate its own corresponding attachment preference factor (AF)
36 based on the corresponding number (N) 40 of attached wireless
network nodes, the corresponding signal strength (S) detected from
the corresponding attachment access point, and the corresponding
depth (D) 44 of the mesh access point. The depth (D) 44 refers to
the distance of the mesh access point 12 relative to the
centralized access point 16, expressed for example as a number of
hops. Although FIG. 1 illustrates the mesh access points (e.g.,
"P1", "P2", "P3", "P4", and "P5") 12 each having the depth of one
hop from the centralized access point 16, another wireless network
node 14 implemented as a mesh access point (e.g., "C3") can
generate its own corresponding attachment preference factor (AF) 36
based on its corresponding number (N) 40 of attached nodes (not
shown), the corresponding signal strength (S) detected from its
corresponding attachment access point "P1" 12, and its
corresponding depth (D) 44 of two hops from the centralized access
point 16. Any mesh access point (not shown) attached to the mesh
access point "C3" also can calculate its own corresponding
attachment preference factor (AF) 36 based on its corresponding
depth (D) 44 of three hops from the RAP 16, etc.
[0042] As illustrated in FIG. 3, the attachment preference
calculation circuit 32 can monitor in step 68 for any increase in
the number (N) 40 of attached wireless network nodes, and can
increase the attachment preference factor (AF) 36 accordingly;
similarly, the attachment preference factor (AF) 36 can be adjusted
based on changes in the signal strength (S) for the corresponding
attachment access point, or a change in the depth by the mesh
access point 12 (e.g., by attaching to a new attachment access
point having a different depth relative to the prior attachment
access point). Hence, if additional wireless network nodes begin
attaching to the mesh access point "P1" 12, the attachment
preference calculation circuit 32 increases in step 70 the
attachment preference factor (AF) 36 accordingly, resulting in a
greater probability that additional wireless network nodes will
attach to the mesh access point "P1" 12; conversely, if the
attachment preference calculation circuit 32 detects a decrease in
the number (N) 40, the attachment preference calculation circuit 32
can decrease in step 70 the attachment preference factor (AF) 36
accordingly, resulting in a lesser probability that additional
wireless network nodes will attach to the mesh access point "P1"
12, and a greater probability that the currently-attached wireless
network nodes may migrate to another mesh access point.
[0043] Consequently, the wireless network nodes 14 can
automatically cluster toward mesh access points (e.g., "P1", "P3",
and "P5") having a larger number of attached wireless network nodes
14, and avoid the other mesh access points having few or no
attached wireless network nodes 14. As illustrated in FIG. 3, if in
step 74 the network interface circuit 30 of a mesh access point 12
receives a broadcast or multicast packet from the centralized
access point 16, the attachment preference calculation circuit 32
determines in step 76 whether there are any attached wireless
nodes, based on the stored number of attached wireless nodes 40.
For example, in the case of the mesh access point "P1" 12, in
response to the corresponding attachment preference calculation
circuit 32 detecting a nonzero number of attached wireless nodes
14, the attachment preference calculation circuit 32 can cause the
wireless network interface circuit 30 to retransmit in step 80 the
broadcast packet or multicast packet for the attached wireless
nodes 14. In the case of the mesh access points "P2" or "P4", since
in step 76 the corresponding attachment preference calculation
circuit 32 determines there are no attached nodes, the
corresponding attachment preference calculation circuit 32 can
suppress in step 78 the retransmission of the broadcast or
multicast packet in order to avoid interference with other mesh
access points (e.g., "P1", "P3", "P5") that have attached wireless
network nodes 14.
[0044] According to the example embodiments, mesh access points can
automatically determine their own attachment preference factors
based on the number of attached wireless network nodes. Hence,
wireless network nodes can selectively attach to the mesh access
points advertising the highest attachment preference factors, and
migrate away from other mesh access points advertising lesser
attachment preference factors. Consequently, redundant mesh access
points within overlapping transmission areas and without any
attached wireless network nodes can be configured to suppress
transmission of multicast packets that may interfere with other
mesh access points.
[0045] While the example embodiments in the present disclosure have
been described in connection with what is presently considered to
be the best mode for carrying out the subject matter specified in
the appended claims, it is to be understood that the example
embodiments are only illustrative, and are not to restrict the
subject matter specified in the appended claims.
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